The present invention relates to the field of ultrasound imaging and, more particularly, to augmented reality visualization of ultrasound images and to the freezing of ultrasound images both in time and in space.
Ultrasound scanners capture live 2D images from within objects or patients. Typically, scanners have a standard option to freeze an image in time and display the still image on the screen for evaluation, such as for example, for measuring spatial dimensions in the image.
Augmented Reality visualization of ultrasound images means that the ultrasound images are displayed as an overlay onto a view of the real object that is being scanned. The overlay is performed in a way such that the ultrasound images appear in the actual scan plane. Structures seen in the ultrasound image are registered to the corresponding real structures and appear in the actual spatial location of these physical structures. Preferably, the AR visualization is stereoscopic to give the user 3D perception.
FIG. 1 show a schematic block diagram of an augmented reality system as may be utilized in conjunction with features of the invention. A tracker camera 10 is coupled by way of and A/D (analog to digital) converter 12 to a programmable digital computer 14. Two scene cameras 16 are coupled to computer 14. An ultrasound scanner 16, having a transducer 18, is coupled by way of an A/D converter 20 to computer 14. A head-mounted display (HMD) control unit 22 is coupled for signal interchange with computer 14 and to an HMD display 24.
Augmented Reality visualization of ultrasound images has been proposed in the literature; see for exampled, M. Bajura, H. Fuchs, and R. Ohbuchi. xe2x80x9cMerging Virtual Objects with the Real World: Seeing Ultrasound Imagery within the Patient.xe2x80x9d Proceedings of SIGGRAPH ""92 (Chicago, Il., Jul. 26-31, 1992). In Computer Graphics 26, #2 (July 1992): 20
Ultrasound scanners are commonly utilized to capture live 2D images from within objects or patients. Scanners typically have a standard option to freeze an image in time and display the still image on the screen for evaluation, e.g. for measuring spatial dimensions in the image.
Helpful background material on augmented reality and related topics can be found in Proceedings of the IEEE and ACM International Symposium on Augmented Reality 2000, dated Oct. 5-6, 2000; Munich, Germany; IEEE Computer Society, Los Alamitos, Calif., U.S.A. In the above-cited Proceedings, an article of particular interest entitled AUGMENTED WORKSPACE: DESIGNING AN AR TESTBED is published on pages 47-53, and is authored by Frank Sauer, an inventor in the present application, et alii.
See also the review article by R. T. Azuma: xe2x80x9cA Survey of Augmented Realityxe2x80x9d, Presence: Teleoperators and Virtula Environments, 6(4), 355-386, (1997).
It has also been proposed to build up 3D volume information from a set of ultrasound images. In conjunction with augmented reality visualization, it has been proposed and demonstrated not to only show the current ultrasound image in the augmented view, but to let each ultrasound image stay (at its correct location) for a while, letting it fade away over a defined time period. As long as the ultrasound transducer is being moved, there would always be a set of different ultrasound images that are being displayed simultaneously. This method is helpful to provide the user with some kind of 3D perception of the scanned volume, but it requires the user to keep moving the transducer so as not to lose the image of the structures of interest.
It is herein recognized that, at least in principle, one might keep all the ultrasound images, building up a permanent 3D ultrasound image. However, this is recognized to be computationally very demanding and, furthermore, it is likely to be confusing to the user, with the display of too many structures.
In accordance with an aspect of the present invention, selected ultrasound images are made stay in the augmented image on a trigger signal, and are made disappear on a trigger signal.